An interdisciplinary group has been established at the Pennsylvania State University for the purpose of developing an improved implantable artificial heart. It is proposed to further develop and refine an artificial heart suitable for calf implantation that is composed of a smooth surface, flexible polyurethane sac within a rigid polysulfone housing. Bjork-Shiley type disc valves will be employed. The pumps will be thoroughly tested on the mock circulatory loop to evaluate their functional characteristics. Simultaneously, an automatic control system is being developed which is based on the maintenance of arterial pressure within a preset band by the control of the rate of the left ventricle. The right ventricle control is based on left atrial pressure and the output of the right ventricle is maintained at a level that will insure a left atrial pressure within normal range. After thorough mock circulatory loop testing, the artificial heart system will be employed in a series of calves. The artificial heart will be implanted with the calf on the heart-lung machine. Each animal will then be returned to a specially developed intensive care unit. Careful hemodynamic, hematologic, and chemical monitoring will be continued for the duration of the study. Special attention will be directed to prevention of thrombus formation, maintenance of central venous pressure within normal range, and threadmill exercise studies. Our past experience with the device under study would suggest that the device is free of thrombo-embolic complications, that a central venous pressure can be maintained within the normal range, and that the control system will permit an increase in cardiac output with exercise. Developmental studies will continue to employ a small brushless, direct current motor to power the artificial heart. Particular attention will be directed to control and balance the artificial heart and to reduction in overall size.